The invention relates to improvements made to sections made of plastomer of U cross-section, which are intended especially for fitting to projecting edges of automobile bodywork or the like.
Such sections generally have an internal metal reinforcement sheathed with a polymer. They are intended to cover external metal edges of bodywork, either to hide them from sight and then to act as an embellisher, or to serve as a fastener for a sealing member, for example of tubular shape, which is integrally attached thereto and intended to be distorted by compression between a door frame and the associated door. In addition, these sections generally have one or more external lips for the purpose of embellishment or sealing.
As an example, a section of this type is shown in cross-section on the single figure of the attached drawing.
Shown therein is the body 1 of the section made of elastomer of U cross-section, equipped with an internal metal reinforcement 2. On one side of the body 1 there is provided a tubular section 3, forming a bead, for example made of cellular rubber, intended to serve as a sealing member between a door and the associated door frame, whereas a lip 4 referred to as "cosmetic" projects outwards on the other side of the section and acts merely as embellishment. The body 1, the section 3 and the lip 4 can be produced in a single stage by coextrusion.
These sections of U cross-section must naturally firmly clamp the metal edge which they cover and, to this end, lips 5 usually project on the opposed inner faces of the arms of the body 1 of U cross-section. These lips 5 are inclined so as to be capable of retracting when the section is placed in position and, on the contrary, of resisting the tearing away of the latter once the section is fitted on the metal edge. These lips 5 may be identical or different and may be arranged symmetrically or otherwise in relation to the median lengthwise plane of the section. They can also be made of the same material as that of the body 1 of the section or of a different material which is coextruded with the latter.
It is rather this second solution which is usually adopted, because it is thus possible to employ for making these lips a material which is better suited to their function. There is therefore a tendency, these days, in order to produce the lips 5, to employ a relatively soft plastic which makes the section easier to place in position, and whose friction coefficient is high, in order to resist the tearing away of the section. Plastics which exhibit these properties and which are employed for this purpose are, for example, the following ones: plasticized polyvinyl chloride or blends of plasticized polyvinyl chloride with compatible polymers, especially natural rubber.
However, they exhibit the disadvantage of deforming when heated, and this constitutes a grave handicap when the vehicles fitted with such sections remain in the sun for long hours during the summer months. To avoid lessening of the clamping action of the section it is therefore necessary to resort to fitting adhesive tapes which bond it to the metal edge to which it is fitted, but this solution is naturally very costly.
The present invention is aimed at remedying these disadvantages.